Re: Dynamic compilation/linking

Steve Boswell <whatis@ucsd.edu> writes:
>[Compile to C, then compile and dynamically-link C.
> Can this be done portably?]


The moderator (John Levine) writes:
>[No, but there may be things that can be ported easily.]


Many LISP systems (e.g., KCL) do what you want. So if you can find a LISP
that works on all of your target platforms, you're in business. See also
the GNU dynamic linker `dld' and the man pages for `ld' for Your Favorite
System(tm). Problems you're likely to find are:


  * There are differnt models for linking.
  * Some systems prohibit dynamic linking (only a few).
  * Some tools are broken.


Note also that dynamic linking can be divided in to various phases:
modifying the object code for its final placement in the address space,
modifying other parts of the address space (e.g., if you're installing
|_printf| dynamically, you generally need to rebind all sites that call
|_printf|). So e.g., `ld' will relocate an object, but it's up to you to
update all call sites for that object.


Be careful, also, that the compile/link cycle is usually slow enough that
it's a performance problem for interactive systems if e.g., each line
entered by the user is compiled and linked using the standard tool.


My own contribution here is _A Portable Interface for On-The-Fly
Instruction Space Modifciation_, Proceedings of ASPLOS-IV, 1991. The
paper describes a portable interface for managing I-cache coherency, but
assumes the existance of a dynamic linker for doing relocation.


;-D on ( Enteractive ) Pardo
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